A majority (58%) also have unfavorable views of the Republican party. But Democrats should not be breaking out the champagne either. Just 43% view that party favorably, and 4 in 10 said they are not sure they'll be voting for either party's candidates in the upcoming midterm elections.

That could be bad news for Democrats looking to make big gains in the midterms, the study noted, since millennials are a key voting bloc for the party.

The survey was conducted Aug. 31-Sept. 16 among 1,816 adults 18-34. It has a margin of error of plus or minus 3.8 percentage points.

GenForward is a new survey partner for NBC, which also teams up with The Wall Street Journal and SurveyMonkey on polling.